Semiconductor device and method of manufacturing the same

ABSTRACT

A semiconductor device includes a semiconductor substrate, and an electrical fuse provided on the semiconductor substrates. The electrical fuse includes a first fuse link and a second fuse link mutually connected in series, a first current inlet/outlet terminal (first terminal) and a second current inlet/outlet terminal (second terminal) respectively provided at an end and the other end of the first fuse link, and a third current inlet/outlet terminal (second terminal) and a fourth current inlet/outlet terminal (third terminal) provided at an end and the other end of the second fuse link.

This application is based on Japanese patent application No.2005-243346, the content of which is incorporated hereinto by reference.

BACKGROUND

1. Technical Field

The present invention relates to a semiconductor device and a method ofmanufacturing the same, and more particularly to a semiconductor deviceincluding an electrical fuse or an antifuse, and a method ofmanufacturing such semiconductor device.

2. Related Art

Semiconductor devices that include a fuse are known in the art, in whichdisconnecting the fuse enables adjusting a value of a resistanceemployed in the semiconductor device, and isolating a defective elementto substitute with a normal element.

Methods of disconnecting the fuse include laser irradiation on a pointto be disconnected of the fuse. JP-A No.H11-297837 discloses a techniqueof solving the following problem arising in the fuse disconnected by thelaser irradiation. With the ongoing micronization of the design ruleswith respect to the semiconductor devices, interconnects to bedisconnected are becoming finer. Accordingly, a laser repair apparatusemployed for disconnecting a fuse interconnect is required to offerhigher positioning accuracy for the laser irradiation. However,employing a brand new apparatus for each product of a newer generationonly leads to continuous increase in manufacturing cost. JP-ANo.H11-297837 proposes, therefore, a circuit configuration including aplurality of interconnects to be disconnected for switching an internalcircuit, to thereby switch the circuit once any of the plurality ofinterconnects is disconnected, as a method of surely disconnecting thefuse interconnect with a one-generation older laser repair apparatus ofinsufficient positioning accuracy. According to the literature, suchconfiguration reduces imperfect switching of the circuit arising fromdefective disconnection due to a shift of the laser irradiation positionon the interconnect to be disconnected.

Apart from such method of disconnecting the fuse by laser irradiation, amethod of disconnecting the fuse with a current is also known, asdisclosed in JP-A No. 2005-39220 and JP-A No. 2005-57186. JP-A No.2005-39220 discloses a fuse that can be melted with a smaller current.In JP-A No. 2005-39220, the conductor constituting the fuse is shaped soas to be folded back a plurality of times.

FIG. 12 is a plan view showing the fuse disclosed in JP-A No.2005-39220. According to FIG. 12, the fuse 1100 is folded back twice.

The fuse 1100 includes a current inlet terminal 1101 and a currentoutlet terminal 1102, and a first linear portion 1103, a second linearportion 1104, and a third linear portion 1113 between the terminals. Thefuse 1100 further includes a first perpendicular connecting portion 1106connecting the first linear portion 1103 and the second linear portion1104, and a second perpendicular connecting portion 1107 connecting thethird linear portion 1113 and the second linear portion 1104.

In the fuse 1100 thus configured, when a predetermined current runs fromthe current inlet terminal 1101 to the current outlet terminal 1102,heat generated in a hatched section 1108 outside the fuse 1100 is addedto heat generated in a hatched section 1109 inside the fuse 1100, tothereby accelerate the fusing of the second linear portion 1104interposed between the hatched section 1109. Thus, the fuse 1100 can beeasily melted apart.

JP-A No. 2005-57186 discloses a fuse in which a point to be melted apartis surrounded by a plate, such that the heat generated at thedisconnection point is detained or accumulated in the vicinity thereof.

In addition, JP-A No. 2004-214580 discloses a fuse layout including aninterconnect electrode having a barrier metal layer constituted of ametal having a high melting point and a main interconnect metal layer.The layout includes a plurality of melting type fuse units connected inseries and a plurality of fuse pads that supplies a current to eachmelting type fuse. In this layout, when at least one of the fuse unitsis disconnected, the entire layout becomes disconnected. Accordingly,imperfect disconnection can be significantly reduced.

As shown in FIG. 12, in the fuse that can be disconnected by a current(E fuse, hereinafter referred to as electrical fuse), supplying apredetermined current from the current inlet terminal 1101 to thecurrent outlet terminal 1102 enables disconnecting the electrical fuse.The electrical fuse can be disconnected by applying a voltage to a pointbetween the current inlet terminal and the current outlet terminal ofthe electrical fuse to be disconnected, and is hence free from theproblem originating from the positioning accuracy incidental to thelaser irradiation for disconnecting the fuse.

However, the present inventors have discovered that the electrical fusemay incur a new problem.

SUMMARY OF THE INVENTION

The present inventors have discovered that, with respect to theelectrical fuse, when the electric fuse is subjected to heat treatmentafter being once disconnected the electrical fuse may be reconnected atthe disconnected position. In the case where the electrical fuse isconstituted of a material susceptible to electromigration, the materialmay migrate because of the electromigration when the semiconductordevice is subjected to the heat treatment after the disconnection of theelectrical fuse, thus causing reconnection at the disconnected point. Ifsuch reconnection takes place, although the electrical fuse to bedisconnected is once disconnected a subsequent inspection cannot providea correct result on whether the electrical fuse is disconnected.

Also the antifuse may, as in the case of the electrical fuse, bedisconnected again because of the migration of the material constitutingthe antifuse, when the antifuse is subjected to heat treatment after theconnection thereof.

Actually the probability that the foregoing reconnection orredisconnection takes place is not critically high, and hence theproblem might be regarded as negligible when the semiconductor device isput to use under a normal condition. However, in the case where thesemiconductor device is required to provide extremely high accuracy orused under a severe condition, the ability of the electrical fuse tomaintain the disconnected state after being disconnected, and theability of the antifuse to maintain the connected state after beingelectrically connected have to be increased.

Further, taking into consideration the possibility that the foregoingreconnection or redisconnection may take place, it is desirable toensure, immediately after disconnecting (or connecting) the fuse, that aplurality of fuses is duly disconnected (or connected) respectively,from the viewpoint of upgrading the reliability of the semiconductordevice when put to practical use.

According to the present invention, there is provided a semiconductordevice including:

a semiconductor substrate, and an element provided on the semiconductorsubstrate and including a state-changing portion that changes adisconnected state or a connected state by applying a current or avoltage,

wherein the element includes:

a first state-changing portion and a second state-changing portion,

a first current inlet/outlet/voltage-applying terminal and a secondcurrent inlet/outlet/voltage-applying terminal respectively provided atan end and the other end of the first state-changing portion,

a third current inlet/outlet/voltage-applying terminal and a fourthcurrent inlet/outlet/voltage-applying terminal respectively provided atan end and the other end of the second state-changing portion,

a decision unit that decides whether the first state-changing portionand the second state-changing portion are both disconnected, and outputsa result of a decision, and

the first state-changing portion and the second state-changing portionare connected so as to allow detecting a change of a state of theelement when at least one of the first state-changing portion and thesecond state-changing portion charges.

Herein, the “element” may be an electrical fuse or an antifuse. When the“element” is the electrical fuse, the “state-changing portion” may be afuse link. In this case, the first state-changing portion and the secondstate-changing portion are connected in series. When the “element” isthe antifuse, the “state-changing portion” may be a link portion to beelectrically connected by application of a voltage. In this case, thefirst state-changing portion and the second state-changing portion areconnected in parallel.

The semiconductor device thus constructed enables, when changing thestate-changing portion in the element, surely changing both of the twostate-changing portions, and allows detecting, when performing thedetection of the state of the element, that the state of the element haschanged if either of the two state-changing portions remains in thechanged state, even though the other of the two state-changing portionshas restored to the original state. Thus, the structure upgrades theability of the element to maintain the state.

According to the present invention, there is provided a semiconductordevice including:

a semiconductor substrate, and an electrical fuse provided on thesemiconductor substrate,

wherein the electrical fuse includes:

a first fuse link and a second fuse link connected in series,

a first current inlet/outlet terminal and a second current inlet/outletterminal respectively provided at an end and the other end of the firstfuse link,

a third current inlet/outlet terminal and a fourth current inlet/outletterminal respectively provided at an end and the other end of the secondfuse link, and

a decision unit that decides whether the first fuse link and the secondfuse link are both disconnected, and outputs a result of a decision.

The electrical fuse stands for a fuse that can be disconnected byapplying a current or a voltage. The fuse link means the portion to bedisconnected in the electrical fuse. The first fuse link and the secondfuse link are both designed so as to be disconnected when a currentexceeding a predetermined value is supplied thereto. Here, whether theelectrical fuse is disconnected is detected depending on whether the twofuse links connected in series are disconnected.

In an embodiment of the present invention, the decision unit may decidewhether both of the first fuse link and the second fuse link aredisconnected, and output the result of the decision. Such arrangementenables deciding, immediately after disconnecting the fuse, whether thetwo fuse links are both duly disconnected. Therefore, the premise that aplurality of fuse links is surely disconnected can be established, eventhough the foregoing reconnection may ever take place, which results inupgraded reliability of the product when put to practical use.

In the semiconductor device according to the present invention, sincethe two fuse links included in the electrical fuse are connected inseries, the current that has passed through the two fuse links in theelectrical fuse can be detected. Accordingly, although one of the twofuse links is reconnected, the electrical fuse can be detected as beingdisconnected, as long as the other fuse link remains disconnected. Suchstructure reduces the reconnection probability significantly, or by aunit of a square, in comparison with an electrical fuse including onlyone fuse link. Here, the “reconnection probability” means thepossibility that the fuse link in the disconnected electrical fusebecomes reconnected, so that the electrical fuse is detected as beingconnected. The foregoing structure, therefore, allows increasing theability of the electrical fuse to maintain its state in thesemiconductor device.

The present invention aims, unlike the technique disclosed in JP-ANo.H11-297837, at significantly reducing the reconnection probability inthe electrical fuse, and thus increasing the ability thereof to maintainits state. To reduce the reconnection probability, the two fuse linksare required to be surely disconnected in the electrical fuse, upondisconnecting the fuse links. If only either of the two fuse links isdisconnected upon disconnecting the electrical fuse, the reconnectionprobability of the electrical fuse cannot be reduced.

The two fuse links included in the electrical fuse may be configuredsuch that one of the fuse links can be disconnected irrespective ofwhether the other fuse link is disconnected. In the semiconductor deviceaccording to the present invention, since the two fuse links in theelectrical fuse are provided with the current inlet terminal and thecurrent outlet terminal at the respective ends thereof, a voltage can beindependently applied to the ends of the respective fuse links. Unlessthe electrical fuse is thus configured to allow independent applicationof a voltage to the respective fuse links, the both of the two fuselinks cannot be surely disconnected though the electrical fuse includestwo fuse links. For example, in the case where the electrical fuse isconfigured such that a voltage is collectively applied to the two fuselinks connected in series from the outer sides, if one of the fuse linksis first disconnected, the current is kept from flowing through theother fuse link, resulting in failure in disconnecting the other fuselink. According to the present invention, since the two fuse linksincluded in the electrical fuse are provided with the current inletterminal and the current outlet terminal at the respective ends thereof,each of the two fuse links in the electrical fuse can be surelydisconnected.

Further, the semiconductor device according to the present inventionincludes the decision unit. The decision unit decides whether each ofthe two fuse links is disconnected. Here, when the probability ofreconnection of one of the fuse links due to a change over time isdenoted by p (0<p≦1), the probability of reconnection of all the npieces of fuses is p^(n). Accordingly, when the decision unit outputs anegative result (i.e. when one of the fuse links is not disconnected),executing the disconnection again to ensure that both of the two fuselinks are disconnected reduces the probability that the change over timeaffects an output of a signal output unit that outputs whether theelectrical fuse is disconnected state or not. In other words, theprobability of the change over time of the fuse is substantiallyreduced.

The electrical fuse may take various structure provided that the firstfuse link and the second fuse link are configured such that a voltagecan be independently applied to each thereof, and hence one of theterminals of the first fuse link and one of the terminals of the secondfuse link may be structured by one and the same terminal. For example,the second current inlet/cutlet terminal and the third currentinlet/outlet terminal may be structured by one and the same terminal.Such configuration still enables surely disconnecting the first fuselink and the second fuse link.

Also, the first fuse link and the second fuse link may be connected inseries via a switch element such as a transistor. For example, the firstfuse link may be connected to one of the source/drain of the transistor,and the second fuse link may be connected to the other of thesource/drain. Under such configuration, when disconnecting the firstfuse link and the second fuse link, the transistor may be turned off tothereby disconnect each of the first fuse link and the second fuse link,and when detecting the disconnection state of the electrical fuse, thetransistor may be turned on so as to detect the current that has passedthrough the first fuse link and the second fuse link.

According to the present invention, there is provided a method ofmanufacturing a semiconductor device including a semiconductorsubstrate, and a plurality of electrical fuses provided on thesemiconductor substrate and respectively including a first fuse link anda second fuse link connected in series, including:

selecting the electrical fuse to be disconnected,

disconnecting the first fuse link and the second fuse link respectivelyin the electrical fuse selected in the step of selecting the electricalfuse,

detecting a connection state of the electrical fuse after the step ofdisconnecting the first fuse link and the second fuse link, and

deciding whether the first fuse link and the second fuse link are bothdisconnected, and outputting a result of a decision.

The method thus arranged allows surely disconnecting each of the firstfuse link and the second fuse link. Here, the step of disconnecting thefirst fuse link and the second fuse link may include supplying a currentfrom an end to the other end of the first fuse link thus to disconnectthe first fuse link, and supplying a current from an end to the otherend of the second fuse link thus to disconnect the second fuse link. Thedisconnecting the first fuse link and the disconnecting the second fuselink may be performed sequentially or at a time, as long as the firstfuse link and the second fuse link can be independently disconnected.

According to the present invention, there is provided a semiconductordevice including:

a semiconductor substrate, and an antifuse provided on the semiconductorsubstrate,

wherein the antifuse includes:

a first link portion and a second link portion connected in parallel,and to be electrically connected by respectively applying apredetermined voltage,

a first voltage-applying terminal and a second voltage-applying terminalrespectively provided at an end and the other end of the first linkportion,

a third voltage-applying terminal and a fourth voltage-applying terminalrespectively provided at an end and the other end of the second linkportion, and

-   -   a decision unit that decides whether the first link portion and        the second link portion are both connected, and outputs a result        of a decision.

The link portion stands for the portion to be connected in the antifuse.Here, the antifuse may take various structure provided that the firstlink portion and the second link portion are connected in parallel atleast when detecting whether the antifuse is connected.

In the semiconductor device according to the present invention, sincethe two link portions included in the antifuse are connected inparallel, the current that has passed through either of the two linkportions in the antifuse can be detected. Accordingly, although one ofthe two link portions is redisconnected, the antifuse can be detected asbeing connected, as long as the other link portion remains connected.Such structure reduces the redisconnection probability by a unit of asquare, in comparison with an antifuse including only one link portion.Here, the “redisconnection probability” means the possibility that thelink portion in the electrically connected antifuse becomesredisconnected, so that the antifuse is detected as being disconnected.The foregoing structure, therefore, allows increasing the ability of theantifuse to maintain its state in the semiconductor device.

In the case of the antifuse also, to reduce the redisconnectionprobability, the two link portions are required to be surely connectedin the antifuse, upon connecting the link portions. In the semiconductordevice according to the present invention, since the two link portionsincluded in the antifuse are provided with the voltage-applying terminalat respective ends thereof, the voltage can be independently applied toeach of the two link portions. Thus, each of the link portions in theantifuse can be surely connected.

According to the present invention, there is provided a method ofmanufacturing a semiconductor device including a semiconductorsubstrate, and a plurality of antifuses provided on the semiconductorsubstrate, and respectively including a first link portion and a secondlink portion connected in parallel and to be electrically connected byrespectively applying a predetermined voltage, including:

selecting the antifuse to be connected,

electrically connecting the first link portion and the second linkportion respectively in the antifuse selected in the step of selectingthe antifuse,

detecting a connection state of the antifuse with the first link portionand the second link portion being connected in parallel, after the stepof electrically connecting the first link portion and the second linkportion, and

deciding whether the first link portion and the second link portion areboth connected, and outputting a result of a decision.

The method thus arranged allows surely connecting each of the first linkportion and the second link portion. Here, the step of connecting thefirst link portion and the second link portion respectively may includeapplying a voltage from an end to the other end of the first linkportion thus to connect the first link portion, and applying a voltagefrom an end to the other end of the second link portion thus to connectthe second link portion. The step of connecting the first link portionand connecting the second link portion may be performed sequentially orat a time, as long as each of the first link portion and the second linkportion can be independently connected.

Thus, the present invention can increase the ability of an electricalfuse or an antifuse to maintain its state.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other objects, advantages and features of the presentinvention will be more apparent from the following description taken inconjunction with the accompanying drawings, in which:

FIG. 1 is a plan view showing a configuration of a semiconductor deviceincluding an electrical fuse according to an embodiment of the presentinvention;

FIGS. 2A to 2C are schematic diagrams for explaining a disconnectionprocess of the electrical fuse shown in FIG. 1 by applying a current;

FIG. 3 is a circuit diagram of a circuit for controlling a potentiallevel in which the electrical fuse shown in FIG. 1 is introduced;

FIGS. 4A and 4B are plan views showing variations of the electrical fuseaccording to the embodiment of the present invention;

FIG. 5 is a plan view showing another variation of the electrical fuseaccording to the embodiment of the present invention;

FIG. 6 is a plan view showing still another variation of the electricalfuse according to the embodiment of the present invention;

FIG. 7 is a plan view showing still another variation of the electricalfuse according to the embodiment of the present invention;

FIG. 8 is a circuit diagram of another electrical fuse;

FIG. 9 is a circuit diagram of another circuit for controlling apotential level in which the electrical fuse shown in FIG. 1 isintroduced;

FIG. 10 is a circuit diagram of an antifuse according to the presentinvention;

FIG. 11 a circuit diagram of another antifuse according to the presentinvention;

FIG. 12 is a plan view showing a conventional electrical fuse;

FIG. 13 is a schematic diagram showing a configuration of asemiconductor device including a circuit for disconnecting an electricalfuse;

FIG. 14 is a table showing decision results and signals to be output bya decision circuit after a disconnection process;

FIG. 15 is a table showing decision results and signals to be output bya decision circuit during the use; and

FIG. 16 is a circuit diagram of a semiconductor device including acircuit for connecting an antifuse.

DETAILED DESCRIPTION

The invention will be now described herein with reference toillustrative embodiments. Those skilled in the art will recognize thatmany alternative embodiments can be accomplished using the teachings ofthe present invention and that the invention is not limited to theembodiments illustrated for explanatory purposes.

FIG. 1 is a plan view showing a configuration of a semiconductor deviceincluding an electrical fuse according to the embodiment of the presentinvention.

In this embodiment, the semiconductor device 100 includes asemiconductor substrate (not shown), an insulating layer 102 provided onthe semiconductor substrate, and an electrical fuse 200 provided on/inthe insulating layer. The electrical fuse 200 includes a first fuse link202 and a second fuse link 204 mutually connected in series, a firstterminal 206, a second terminal 208, and a third terminal 210. The firstfuse link 202 and the second fuse link 204 are both constituted of aconductive material, and designed so as to be disconnected (cut) when acurrent exceeding a predetermined value is supplied thereto.

The first terminal 206 and the second terminal 208 are respectivelyprovided at an end and the other end of the first fuse link 202, andserve as a current inlet terminal and a current outlet terminal whendisconnecting the first fuse link 202 by applying a current. The secondterminal 208 and the third terminal 210 are respectively provided at anend and the other end of the second fuse link 204, and serve as acurrent inlet terminal and a current outlet terminal (or a current inletterminal) when disconnecting the second fuse link 204 by applying acurrent. In this embodiment, the current outlet terminal of the firstfuse link 202 and the current input terminal (or a current outletterminal) of the second fuse link 204 are one and the same terminal (thesecond terminal 208).

In this embodiment, the first fuse link 202 and the second fuse link 204may be constituted of a copper-containing metal layer predominantlycomposed of copper. The copper-containing metal layer may containsilver. Further, the copper-containing metal layer may contain one or aplurality of dissimilar elements selected out of the group consisting ofAu, Pt, Cr, Mo, W, Mg, Be, Zn, Pd, Cd, Hg, Si, Zr, Ti, and Sn.

In this embodiment, the insulating layer 102 may be any of thoseinsulating layers provided on the semiconductor substrate, and examplesthereof include an element isolation insulating layer, one of interlayerdielectrics among a multilayer interconnect structure, and an insulatinglayer formed on a bottom portion of a trench.

Referring now to FIGS. 2A to 2C and 13, a process for disconnecting theelectrical fuse 200 thus configured with a current will be describedhereunder. Here, the first fuse link 202 and the second fuse link 204can be independently supplied with a voltage. In other words, either ofthe first fuse link 202 or the second fuse link 204 can be disconnectedirrespective of whether the other thereof is disconnected.

FIG. 13 is a schematic diagram showing a configuration of thesemiconductor device 100 including a circuit for disconnecting theelectrical fuse 200.

The semiconductor device 100 further includes a first interconnect 410connected to the first terminal 206, a second interconnect 412 connectedto the second terminal 208, and a third interconnect 414 connected tothe third terminal 210. An end of the first interconnect 410 and thethird interconnect 414 are respectively connected to a voltage source V.An end of the second interconnect 412 is grounded. The other end of thefirst interconnect 410, the second interconnect 412, and the thirdinterconnect 414 are respectively connected to a decision circuit 400.On the first interconnect 410, a first switch 416 (SW1) is providedbetween the first terminal 206 and the voltage source V, and a fourthswitch 422 (SW11) is provided between the first terminal 206 and thedecision circuit 400, respectively. Likewise, on the second interconnect412, a second switch 418 (SW2) is provided between the second terminal208 and the ground point GND, and a fifth switch 424 (SW12) is providedbetween the second terminal 208 and the decision circuit 400,respectively. Also, on the third interconnect 414, a third switch 420(SW3) is provided between the third terminal 210 and the voltage sourceV, and a sixth switch 426 (SW13) is provided between the third terminal210 and the decision circuit 400, respectively.

Although not shown, the semiconductor device 100 may include a pluralityof electrical fuses 200. Firstly, one of the electrical fuses 200 to bedisconnected is selected. In this embodiment, in the electrical fuse 200selected to be disconnected, the first fuse link 202 and the second fuselink 204 are respectively disconnected.

A process of disconnecting with a current the first fuse link 202 in theelectrical fuse 200 selected to be disconnected will be first described.It is assumed here that the first switch 416 and the second switch 418are turned on, and the other switches are off. Under such state, apredetermined high potential (for example the source voltage VCC) isapplied to the first terminal 206, and a predetermined low potential(ground potential) is applied to the second terminal 208. At this stage,the third terminal 210 is in a floating state and hence the current doesnot run between the second terminal 208 and the third terminal 210.Accordingly, the current runs from the first terminal 206 toward thesecond terminal 208, so that the first fuse link 202 is disconnected.

In another example, the same potential as that given to the secondterminal 208 may be given to the third terminal 210, so as to inhibitthe current from running between the second terminal 208 and the thirdterminal 210. For example, the second terminal 208 and the thirdterminal 210 may be grounded (as shown in FIG. 2A).

Then the decision circuit 400 decides whether the first fuse link 202 isdisconnected. At this stage, the first switch 416 and the second switch418 are turned off, and the fourth switch 422 and the fifth switch 424are turned on. The other switches are kept off. Here, the decisioncircuit 400 detects the resistance value between the first terminal 206and the second terminal 208. The decision circuit 400 may decide thatthe first fuse link 202 is disconnected when the resistance value is notless than a predetermined value (for instance, 1 kΩ).

Now a process for disconnecting the second fuse link 204 with a currentwill be described. Here the second switch 418 and the third switch 420are turned on, and the other switches are off. Under such state, apredetermined high potential (for example the source voltage VCC) isapplied to the third terminal 210, and a predetermined low potential(ground potential) is applied to the second terminal 208. At this stage,the first terminal 206 is in a floating state and hence the current doesnot run between the first terminal 206 and the second terminal 208.Accordingly, the current runs from the second terminal 208 toward thethird terminal 210, so that the second fuse link 204 is disconnected.

In another example, the same potential as that given to the secondterminal 208 may be given to the first terminal 206, so as to inhibitthe current from running between the first terminal 206 and the secondterminal 208. For example, the high potentials may be applied to boththe first terminal 206 and the second terminal 208 and the thirdterminal 210 may be grounded (as shown in FIG. 2B).

Then the decision circuit 400 decides whether the second fuse link 204is disconnected. At this stage, the second switch 418 and the thirdswitch 420 are turned off, and the fifth switch 424 and the sixth switch426 are turned on. The other switches are kept off. Here, the decisioncircuit 400 detects the resistance value between the second terminal 208and the third terminal 210. The decision circuit 400 may decide that thesecond fuse link 204 is disconnected when the resistance value is notless than a predetermined value (for instance, 1 kΩ).

Through the foregoing process, the two fuse links can be surelydisconnected respectively, in the electrical fuse 200.

In this embodiment, the electrical fuse 200 may be configured such thatthe use thereof is permitted only when the decision circuit 400 decides,as a result of the detection, that the first fuse link 202 and thesecond fuse link 204 are both disconnected, immediately after thedisconnection process or before starting to use the electrical fuse 200.The decision circuit 400 may be configured so as to retain the decisionresult on the disconnection state of the first fuse link 202 and thedecision result on the disconnection state of the second fuse link 204.The decision circuit 400 decides whether the first fuse link 202 and thesecond fuse link 204 are both disconnected, and outputs a signalindicating that the electrical fuse 200 is non-defective when both ofthem are disconnected, but outputs a signal indicating that theelectrical fuse is defective, when only one of them is disconnected orwhen neither of them is disconnected. FIG. 14 is a table showing thedecision results and signals to be output by the decision circuit 400after the disconnection process. In FIG. 14, “1” denotes the decision ofbeing disconnected, and “0” denotes the decision of not beingdisconnected (in other words, the decision of being connected). Thedecision circuit 400 outputs the signal “1” indicating that theelectrical fuse 200 is non-defective, only when the decision resultswith respect to the first fuse link 202 and the second fuse link 204 areboth “1”. The decision circuit 400 outputs the signal “0” indicatingthat the electrical fuse 200 is defective, in all the other cases. Inother words, the decision circuit 400 performs an AND decisionimmediately after the disconnection process (and at starting to use theelectrical fuse 200). Such arrangement reduces the probability that thechange over time affects an output of a signal output unit. Thus, theprobability of the change over time of the fuse is substantiallyreduced.

The decision process performed during the use of the electrical fuse 200will now be described hereunder. The decision on whether the electricalfuse 200 is disconnected during the use thereof may be obtained bysupplying a current between the first terminal 206 and the thirdterminal 210. Assuming that, in the configuration shown in FIG. 13, thefourth switch 422 and the sixth switch 426 are turned on, for example apredetermined signal (VCC) is input through the first terminal 206, sothat the signal is output through the third terminal 210. The otherswitches are turned off. Under such state, the decision circuit 400detects a resistance value between the first terminal 206 and the thirdterminal 210.

FIG. 15 is a table showing the decision results and signals to be outputby the decision circuit 400 during the use of the electrical fuse 200.In FIG. 15, “1” denotes the decision of being disconnected, and “0”denotes the decision of not being disconnected. The decision circuit 400outputs the signal “1” indicating that the electrical fuse 200 isdisconnected, when at least one of the decision results with respect tothe first fuse link 202 and the second fuse link 204 is “1”. Thedecision circuit 400 outputs the signal “0” indicating that theelectrical fuse 200 is not disconnected, only when the decision resultswith respect to the first fuse link 202 and the second fuse link 204 areboth “0”. In other words, the decision circuit 400 performs an ORdecision during use of the electrical fuse 200.

Connecting the first fuse link 202 and the second fuse link 204 inseries, as in the electrical fuse 200, 1 enables deciding that theelectrical fuse 200 is disconnected when at least one of the first fuselink 202 and the second fuse link 204 is disconnected. Accordingly, eventhough the first fuse link 202 and the second fuse link 204 may bereconnected owing to a heat treatment performed after the disconnectionof the electrical fuse 200, the reconnection probability of theelectrical fuse 200 can be reduced by a unit of a square. For example,when the reconnection probability of one of the fuse links due to theheat treatment after the disconnection is 1E-4, the reconnectionprobability of the electrical fuse 200 becomes 1E-8 when the electricalfuse 200 includes two fuse links.

In another embodiment, the decision circuit 400 may be engaged incontrolling the application of a voltage for disconnecting the firstfuse link 202 and the second fuse link 204.

FIG. 3 is a circuit diagram of a circuit for controlling a potentiallevel in which the electrical fuse 200 shown in FIG. 1 is introduced.

An end of the electrical fuse 200 on the side of the second fuse link204 is connected to an end of a resistance 220. The other end of theresistance 220 is grounded. Between the second fuse link 204 and theresistance 220, an inverter 230 is connected.

Here, the first terminal 206 receives the source voltage VCC. Under suchcircuit configuration, a high level signal is input to the inverter 230when the electrical fuse 200 is not disconnected. At this moment, theinverter 230 outputs a low level signal. On the other hand, when theelectrical fuse 200 is disconnected, the inverter 230 receives an inputof the low level signal, and outputs a high level signal. Thus, thepotential level of an output destination of the inverter 230 can becontrolled according to the disconnection state of the electrical fuse200.

In this embodiment, since the electrical fuse 200 includes two fuselinks, the reconnection probability can be significantly reduced in theelectrical fuse 200 selected for disconnection and actuallydisconnected. Such structure allows precisely controlling the potentiallevel in the circuit as shown in FIG. 3.

In this embodiment, the first fuse link 202 and the second fuse link 204in the electrical fuse 200 may be formed in various shapes. Someexamples will be cited hereunder.

FIGS. 4A and 4B are plan views showing variations of the electrical fuse200 according to this embodiment.

The first fuse link 202 and the second fuse link 204 may include afold-back portion between the first terminal 206 and the second terminal208, and between the second terminal 208 and the third terminal 210,respectively. Here, “fold back” means that the portion is bent backwardin an angle larger than 90 degrees.

Referring to FIG. 4A, the first fuse link 202 includes a linear portion202 a, a linear portion 202 b, a linear portion 202 c, a connectingportion 202 d connecting the linear portion 202 a and the linear portion202 b, and a connecting portion 202 e connecting the linear portion 202b and the linear portion 202 c. The linear portion 202 a, the linearportion 202 b, and the linear portion 202 c are disposed generally inparallel to one another. The second fuse link 204 includes a linearportion 204 a, a linear portion 204 b, a linear portion 204 c, aconnecting portion 204 d connecting the linear portion 204 a and thelinear portion 204 b, and a connecting portion 204 e connecting thelinear portion 204 b and the linear portion 204 c. The linear portion204 a, the linear portion 204 b, and the linear portion 204 c aredisposed generally in parallel to one another.

Hereinafter, a direction from the first terminal 206 toward the secondterminal 208 will be referred to as a heading direction. The first fuselink 202 is bent to the right from the heading direction by approx. 90degrees at the connection point between the linear portion 202 a and theconnecting portion 202 d, and bent again to the right from the headingdirection by approx. 90 degrees at the connection point between theconnecting portion 202 d and the linear portion 202 b. Accordingly, thefirst fuse link 202 is bent by 180 degrees, i.e. folded back once.Likewise, the first fuse link 202 is bent to the left from the headingdirection by approx. 90 degrees at the connection point between thelinear portion 202 b and the connecting portion 202 e, and bent again tothe left from the heading direction by approx. 90 degrees at theconnection point between the connecting portion 202 e and the linearportion 202 c. Accordingly, the first fuse link 202 is bent again by 180degrees, i.e. folded back one more time. Thus, in the example shown inFIG. 4A, the first fuse link 202 is folded back twice in total. Thesecond fuse link 204, similarly shaped to the first fuse link 202, isalso folded back twice in total.

In the electrical fuse 200 shaped as above, when a predetermined currentruns from the first terminal 206 toward the second terminal 208, heatgenerated outside the first fuse link 202 is added to heat generatedinside the first fuse link 202. Accordingly, the linear portion 202 blocated in a central portion is efficiently heated in particular, andthe disconnection thereof is accelerated. Thus, the first fuse link 202can be disconnected with a smaller current.

Likewise, in the electrical fuse 200, when a predetermined current runsfrom the second terminal 208 toward the third terminal 210, heatgenerated outside the second fuse link 204 is added to heat generatedinside the second fuse link 204. Accordingly, the linear portion 204 blocated in a central portion is efficiently heated in particular, andthe disconnection thereof is accelerated. Thus, the second fuse link 204can be disconnected with a smaller current.

In the example shown in FIG. 4A, the first fuse link 202 and the secondfuse link 204 may be buried in a recess formed in the insulating layer102. Such structure allows the first fuse link 202 and the second fuselink 204 to be more effectively heated when the current is supplied tothe first fuse link 202 and the second fuse link 204, thus furtherfacilitating the disconnection of the first fuse link 202 and the secondfuse link 204.

Alternatively, as shown in FIG. 4B, the connecting portion 202 d, theconnecting portion 202 e, the connecting portion 204 d, and theconnecting portion 204 e may be formed in a curved shape. In FIG. 4Balso, the first fuse link 202 is folded back by 80 degrees at theconnecting portion 202 d, and again folded back by 180 degrees at theconnecting portion 202 e, twice in total. This also applies to thesecond fuse link 204. Such configuration also offers the advantages asthose offered by the example of FIG. 4A.

Folding back thus the first fuse link 202 and the second fuse link 204 aplurality of times in the electrical fuse 200 can locate the centrallinear portion of the plurality of linear portions constituting the fuselink between other linear portions constituting the fuse link and theconnecting portions. Because of such configuration, when a current issupplied to the fuse link, the heat generated in the surrounding linearportions and connecting portions propagates to the central linearportion, thereby keeping the temperature of the central linear portionat a relatively higher level. This facilitates the electromigration ofthe material constituting the fuse link in a high temperature zone, thusfurther urging the disconnection of the fuse link.

FIG. 5 is a plan view showing another variation of the electrical fuse200 according to the embodiment.

In FIG. 5, the first fuse link 202 is folded back four times andincludes a widened portion 232 of a thicker wire in a central linearportion of a plurality of linear portions. The widened portion 232 ismade wider than the linear portions and connecting portions. Providingsuch widened portion 232 leads to an increase in amount of the materialconstituting the first fuse link 202 that migrates in the widenedportion 232, when disconnecting the first fuse link 202 utilizing theelectromigration. Besides, since the widened portion 232 is located at acentral portion of the first fuse link 202, the widened portion 232 ismore efficiently heated. Accordingly, the electromigration can be easilyprovoked at the widened portion 232. This facilitates the disconnectionof the fuse link 202 at a location between the widened portion 232 andthe fold-back portion close thereto.

The second fuse link 204 may also include, as the first fuse link 202, awidened portion 234 of a thicker wire in a central linear portion. Thisfacilitates the disconnection of the second fuse link 204.

FIG. 6 is a plan view showing still another variation of the electricalfuse 200 according to the embodiment.

In FIG. 6, the first fuse link 202 and the second fuse link 204 arerespectively folded back once by 180 degrees.

The first fuse link 202 includes a linear portion 202 a, a linearportion 202 b, and a connecting portion 202 d connecting the linearportion 202 a and the linear portion 202 b. The linear portion 202 a andthe linear portion 202 b are disposed generally in parallel to eachother. The second fuse link 204 includes a linear portion 204 a, alinear portion 204 b, and a connecting portion 204 d connecting thelinear portion 204 a and the linear portion 204 b. The linear portion204 a and the linear portion 204 b are disposed generally in parallel toeach other. The electrical fuse 200 further includes the first terminal206 and a fourth terminal 208 a respectively connected to each end ofthe first fuse link 202, a fifth terminal 208 b and the third terminal210 respectively connected to each end of the second fuse link 204, anda connecting portion 208 c connecting the fourth terminal 208 a and thefifth terminal 208 b.

Hereinafter, a direction from the first terminal 206 toward the fourthterminal 208 a in the first fuse link 202 will be referred to as aheading direction. Also, a direction from the fifth terminal 208 btoward the third terminal 210 in the second fuse link 204 will bereferred to as a heading direction. The first fuse link 202 is bent tothe right from the heading direction by approx. 90 degrees at theconnection point between the linear portion 202 a and the connectingportion 202 d, and again bent to the right from the heading direction byapprox. 90 degrees at the connection point between the connectingportion 202 d and the linear portion 202 b. Accordingly, the first fuselink 202 is bent by 180 degrees, i.e. folded back once. The second fuselink 204 is bent to the right from the heading direction by approx. 90degrees at the connection point between the linear portion 204 a and theconnecting portion 204 d, and again bent to the right from the headingdirection by approx. 90 degrees at the connection point between theconnecting portion 204 d and the linear portion 204 b. Accordingly, thesecond fuse link 204 is bent by 180 degrees, i.e. folded back once.

Here, the linear portions and the connecting portions connected theretoare disposed generally perpendicularly to each other. Such configurationbetter facilitates the disconnection of the first fuse link 202 and thesecond fuse link 204 with a current, than in the case of straightlyaligning the first fuse link 202 and the second fuse link 204.

Further details will be described with respect to the linear portion 202a and the connecting portion 202 d as an example. The linear portion 202a and the connecting portion 202 d are disposed generallyperpendicularly to each other. Accordingly, a less amount of thematerial constituting the first fuse link 202 migrates in suchconnection points, than in the remaining portions. Creating thusdifference in amount of the migrating material constituting the firstfuse link 202 depending on the location facilitates the disconnection ofthe first fuse link 202 at the location where a less amount of materialmigrates, when disconnecting the first fuse link 202 utilizing theelectromigration. This also applies to other connection points, and tothe second fuse link 204 as well.

In the example shown in FIG. 6 also, the connecting portion 202 d andthe connecting portion 204 d may be formed in a curved shape, as in FIG.4B. Such configuration also facilitates reducing the amount of themigrating material constituting the first fuse link 202 and the secondfuse link 204 at the curved portions. This facilitates the disconnectionat the location where a less amount of material migrates.

FIG. 7 is a plan view showing still another variation of the electricalfuse 200 according to the embodiment.

In FIG. 7, the first fuse link 202 and the second fuse link 204respectively include a bent portion 236 and a bent portion 238. Suchconfiguration can also facilitates reducing the amount of the migratingmaterial constituting the first fuse link 202 and the second fuse link204 at the bent portions. This facilitates the disconnection at thelocation where a less amount of material migrates.

Although the embodiments of the present invention have been describedreferring to the drawings, the foregoing embodiments are only exemplaryand various other structures may be employed.

Although the electrical fuse 200 includes two fuse links in theforegoing embodiments, the electrical fuse 200 may include three or morefuse links. In this case also, each fuse link may be provided with apair of terminals at the respective ends, so as to independently receivea voltage. With such configuration, each fuse link of the electricalfuse including a plurality of fuse links can be surely disconnected.Also, the plurality of fuse links may be connected in series. Increasingthus the number of fuse links included in the electrical fuse 200 cansignificantly reduce the reconnection probability.

The plurality of fuse links included in the electrical fuse 200 may beformed in generally the same shape. This facilitates disconnecting thefuse links under the same condition, thereby simplifying the process.

Also, although the first fuse link 202 and the second fuse link 204 areconstituted of a copper-containing metal layer predominantly composed ofcopper in the foregoing embodiments, the present invention is alsoapplicable to the case where the fuse links are constituted of adifferent material, provided that the electromigration provokes thereconnection.

Also, referring to FIG. 8, the first fuse link 202 and the second fuselink 204 may be connected in series via a switch element such as atransistor 240, in the electrical fuse 200. In FIG. 8, the first fuselink 202 is connected to either of the source/drain of the transistor240, and the second fuse link 204 is connected to the other of thesource/drain of the transistor 240. The first fuse link 202 is providedwith the first terminal 206 and the fourth terminal 208 a at therespective ends thereof. The second fuse link 204 is provided with thefifth terminal 208 b and the third terminal 210 at the respective endsthereof. The transistor 240 is located between the fourth terminal 208 aand the fifth terminal 208 b.

In the electrical fuse 200 thus configured, the transistor 240 is turnedoff when disconnecting the first fuse link 202 and the second fuse link204. Under such state, when a predetermined voltage is applied betweenthe first terminal 206 and the fourth terminal 208 a, and between thefifth terminal 208 b and the third terminal 210 respectively, thecurrent is supplied to the first fuse link 202 and to the second fuselink 204, thereby disconnecting those fuse links. For detecting whetherthe electrical fuse 200 is disconnected, the transistor 240 is turnedon, such that a signal input through an input terminal 242 is outputthrough an output terminal 244. Such arrangement enables surelydisconnecting the first fuse link 202 or the second fuse link 204 in thedisconnection process, and detecting that the electrical fuse 200 isdisconnected if one of the fuse links is disconnected in the detectionprocess, thus significantly reducing the reconnection probability of theelectrical fuse 200.

FIG. 9 is a circuit diagram of another circuit for controlling apotential level in which the electrical fuse shown in FIG. 1 isintroduced.

In FIG. 9, whether the electrical fuse is disconnected is decided basedon a combination of two electrical fuses 200. Specifically, an outputfrom the two electrical fuses 200 is input to a NAND circuit 270, andconnected to the inverter 230 via the NAND circuit 270. A respective endof the two electrical fuses 200 on the side of the second fuse link 204is connected to the resistance 220 and the resistance 260.

For example, to put the electrical fuse in a disconnected state underthe combination of the two electrical fuses 200, the first fuse link 202and the second fuse link 204 in the respective electrical fuses 200 aredisconnected. Then when VCC is applied to the respective first terminal206 of the electrical fuses 200, a low level signal is input to the NANDcircuit 270 if at least one of the two electrical fuses 200 isdisconnected. When at least one low level signal is input to the NANDcircuit 270, the NAND circuit 270 outputs a low level signal. In thisexample, the reconnection probability of the respective electrical fuses200 is already significantly reduced, and besides the connection stateis decided based on the combination of the plurality of electrical fuses200. Therefore, the disconnection of the fuse link can be furtherensured.

The present invention is also applicable to an antifuse. The antifusehas a reverse function to the electrical fuse, and becomes electricallyconnected when a voltage is applied thereto. The antifuse may beconstituted of two pieces of conductive materials with an insulatingmaterial interposed therebetween. Under such structure, applying apredetermined voltage between the two conductive materials can provoke adielectric breakdown of the insulating material, thus electricallyconnecting the two conductive materials. Here, the conductive materialmay be constituted of a copper-containing metal layer predominantlycomposed of copper. The antifuse may also incur redisconnection afterbeing once connected, for example by migration of the materialconstituting the conductive material.

FIG. 10 is a circuit diagram of an antifuse 300 according to the presentinvention.

The antifuse 300 includes a first terminal 306, a second terminal 308, athird terminal 310, a first link portion 302 to be connected by avoltage applied between the first terminal 306 and the second terminal308, and a second link portion 304 to be connected by a voltage appliedbetween the third terminal 310 and the second terminal 308. The antifuse300 may also be provided on a semiconductor substrate (not shown) thusto be included in a semiconductor device, as well as the electrical fuse200.

In FIG. 10, the first link portion 302 and the second link portion 304are configured so as to independently receive a voltage, and to beconnected in parallel. The two link portions included in the antifuse300 may be arranged such that one of the link portions can be connectedirrespective of whether the other is connected. For example, theantifuse 300 may be configured such that the two link portions are notelectrically connected or are connected in series when connecting therespective link portions, and that the two link portions are connectedin parallel when detecting the connection. In this example, a switchelement such as a transistor 312 is provided between the first linkportion 302 and the second link portion 304. An end of the first linkportion 302 is connected to one of the source/drain of the transistor312, and an end of the second link portion 304 is connected to the otherof the source/drain of the transistor 312.

Although not shown, the semiconductor device may include a plurality ofantifuses 300. Firstly, one of the antifuses 300 to be connected isselected. In the antifuse 300 selected for connection, the first linkportion 302 and the second link portion 304 are respectivelyelectrically connected. To connect the first link portion 302 in theantifuse 300 to be connected, the transistor 312 is turned off, and apredetermined high potential (VCC) is applied for example to the firstterminal 306, and the second terminal 308 is grounded. At this moment,the third terminal 310 is also grounded so as to keep the second linkportion 304 from receiving a voltage. Thus, the insulating material ofthe first link portion 302 incurs the dielectric breakdown, therebyelectrically connecting the first link portion 302.

Likewise, to connect the second link portion 304, the transistor 312 isturned off, and a predetermined high potential (VCC) is applied forexample to the third terminal 310, and the second terminal 308 isgrounded. At this moment, the first terminal 306 is also grounded so asto keep the first link portion 302 from receiving a voltage. Thus, theinsulating material of the second link portion 304 incurs the dielectricbreakdown, thereby electrically connecting the second link portion 304.

Thereafter, the connection state of the antifuse 300 is detected. Whendetecting the antifuse 300, the transistor 312 is turned on, to achieveconduction between an end of the first link portion 302 and an end ofthe second link portion 304. Accordingly, the first link portion 302 andthe second link portion 304 are connected in parallel. Under such state,a signal input through the input terminal 314 is output through theoutput terminal 316. Such arrangement enables ensuring the connection ofthe first link portion 302 and the second link portion 304 in theconnection process, and detecting, in the detecting process, that theantifuse 300 is connected provided that at least one of the linkportions is connected, thereby significantly reducing theredisconnection probability of the antifuse 300.

FIG. 16 is a circuit diagram of a semiconductor device including acircuit for disconnecting the antifuse 300.

The semiconductor device 100 includes the decision circuit 400, a switch430 provided between the first terminal 306 and the decision circuit400, a switch 432 provided between the second terminal 308 and thedecision circuit 400, and a switch 434 provided between the thirdterminal 310 and the decision circuit 400. The transistor 312 isprovided between the first link portion 302 and the second link portion304. Whether the first link portion 302 is connected can be detectedbased on a current value between the first terminal 306 and the secondterminal 308 by turning on the switch 430 and the switch 432 and turningoff the switch 434 with having the transistor 312 turned off. Likewisewhether the second link portion 304 is connected can be detected basedon a current value between the second terminal 308 and the thirdterminal 310, by turning on the switch 432 and the switch 434 andturning off the switch 430 with having the transistor 312 turned off.The decision circuit 400 decides whether both of the first link portion302 and the second link portion 304 are connected right after theconnection operation of the first link portion 302 and the second linkportion 304. On the other hand, the decision circuit 400 decides whetherat least one of the first link portion 302 and the second link portion304 is connected during use of the electrical fuse 200.

Alternatively, a configuration as shown in FIG. 11 may be adopted.

In FIG. 11, the first link portion 302 is provided with the firstterminal 306 and the second terminal 308 at the respective ends thereof,and the second link portion 304 is provided with the third terminal 310and the fourth terminal 311 at the respective ends thereof. Between anend of the first link portion 302 and an end of the second link portion304, i.e. between the first terminal 306 and the third terminal 310, afirst transistor 312 a is provided. Between the other end of the firstlink portion 302 and the other end of the second link portion 304, i.e.between the second terminal 308 and the fourth terminal 311, a secondtransistor 312 b is provided. When connecting the first link portion 302and the second link portion 304, respectively, the first transistor 312a and the second transistor 312 b may be turned off, and a predeterminedvoltage may be respectively applied between the first terminal 306 andthe second terminal 308, and between the third terminal 310 and thefourth terminal 311, to thereby connect the first link portion 302 andthe second link portion 304 generally at the same time. When detectingthe antifuse 300, the first transistor 312 a and the second transistor312 b may be turned on, so as to connect the first link portion 302 andthe second link portion 304 in parallel.

Although the antifuse 300 includes two link portions in FIGS. 10 and 11,the antifuse 300 may include three or more link portions. In this casealso, each link portion is configured so as to be independentlyconnected, and to be connected in parallel when detecting theconnection.

Meanwhile, the first fuse link 202 and the second fuse link 204according to the present invention may be respectively configured asfollows. Here, it is to be noted that the first fuse link 202 and thesecond fuse link 204 may be formed in various other shapes than thosedescribed hereunder, as long as they are configured to be disconnectedwhen a current of a predetermined value is supplied thereto.

In the semiconductor device according to the present invention, the fuselink may include a first linear portion extending in a first direction,an second linear portion extending in a direction generally opposite tothe first direction, and a third linear portion folded back in the firstdirection electrically connected to one another, and the first linearportion, the second linear portion, and the third linear portion may bedisposed generally in parallel.

Under such structure, one of the first linear portion, the second linearportion, and the third linear portion can be surrounded by the remaininglinear portions, thus to be kept under a relatively higher temperature.Such structure therefore facilitates efficiently disconnecting the fuselink by supplying a current.

In the semiconductor device according to the present invention, the fuselink may include a first linear portion extending 1 n a first direction,a second linear portion extending in a direction generally opposite tothe first direction, a third linear portion folded back in the firstdirection, a first joint linear portion connecting an end of the firstlinear portion and an end of the second linear portion, and a secondjoint linear portion connecting the other end of the second linearportion and an end of the third linear portion, electrically connectedto one another.

In the semiconductor device according to the present invention, the fuselink may include a plurality of first linear portions, respectivelyextending in a first direction and disposed parallel to one another, anda plurality of second linear portions respectively extending in a seconddirection different from the first direction and disposed parallel toone another, and the plurality of first linear portions and theplurality of second linear portions may be disposed such that four sidesof at least one of the first linear portions or one of the second linearportions are surrounded by others of the first linear portion or of thesecond linear portion. Here, the plurality of first linear portions andthe plurality of second linear portions may be electrically connected toone another.

Surrounding thus the four sides of the first linear portion or thesecond linear portion by other linear portions allows keeping thetemperature of the first linear portion or the second linear portionhaving its four sides surrounded at a higher level. Such configurationtherefore facilitates efficiently disconnecting the first linear portionor the second linear portion having its four sides surrounded.

In the semiconductor device according to the present invention, theplurality of first linear portions and the plurality of second linearportions may be disposed such that, when a current runs from an end ofthe fuse link to the other end, the current runs in an oppositedirection in the respective adjacent plurality of first linear portionsand plurality of second linear portions.

Such configuration prevents emergence of a magnetic field thatpenetrates the semiconductor substrate originating from the current,when the current is supplied to the fuse link.

In the semiconductor device according to the present invention, the fuselink may include a plurality of first linear portions respectivelyextending in a first direction and disposed in parallel to one another,a plurality of second linear portions respectively extending in a seconddirection different from the first direction and disposed parallel toone another, a current inlet terminal and a current outlet terminal. Theplurality of first linear portions and the plurality of second linearportions may be disposed such that, when a current runs from the currentinlet terminal to the current outlet terminal, the current runs in anopposite direction in the respective adjacent plurality of first linearportions and plurality of second linear portions.

Such configuration prevents emergence of a magnetic field thatpenetrates the semiconductor substrate originating from the current,when the current is supplied to the fuse link.

In the semiconductor device according to the present invention, the fuselink may include a narrowed portion formed in a smaller width than theremaining portion of the fuse link.

Providing such narrowed portion facilitates efficiently disconnectingthe fuse link at the narrowed portion.

In the semiconductor device according to the present invention, the fuselink may include a widened portion formed in a greater width than theremaining portion of the fuse link.

In the widened portion of the fuse link formed in a greater width, alarger amount of the material constituting the fuse link migratesbecause of the electromigration. Accordingly, disconnection more readilytakes place at a position anterior to the widened portion in a directionopposite to the running direction of the current. Therefore, the fuselink can be easily disconnected.

In the semiconductor device according to the present invention, the fuselink may further include a current inlet terminal and a current outletterminal, and the widened portion may be located between the currentinlet terminal and the fold-back portion. In addition, the widenedportion may be located in the vicinity of the fold-back portion.

At the fold-back portion, a less amount of the material constituting thefuse link is caused to migrate. Accordingly, providing the widenedportion at a location between the current inlet terminal and thefold-back portion facilitates disconnecting the fuse link between thewidened portion and the told-back portion.

In the semiconductor device according to the present invention, thewidened portion may be provided on the side of the current inletterminal. According to the present invention, since the fuse link isfolded back a plurality of times as already stated, the widened portionlocated close to the fuse link is kept under a relatively highertemperature, and is hence easy to be disconnected at a position close tothe widened portion, because of the electromigration.

In the semiconductor device according to the present invention, thewidened portion may be provided at a generally central portion of thefuse link. According to the present invention, since the fuse link isfolded back a plurality of times as already stated, a central portion ofthe fuse link is kept under a relatively higher temperature, and ishence easy to be disconnected. Thus, providing the widened portion at acentral portion of the fuse link facilitates efficiently disconnectingthe fuse link.

According to the present invention, there is provided a semiconductordevice including a semiconductor substrate, a fuse link provided on thesemiconductor substrate to be disconnected by supplying a current, inwhich the fuse link is formed in a bent shape and includes a widenedportion formed in a greater width than the remaining portion of the fuselink.

In the widened portion of the fuse link formed in a greater width, alarger amount of the material constituting the fuse link migratesbecause of the electromigration. Accordingly, providing the widenedportion in the fuse link urges disconnection at a position anterior tothe widened portion in a direction opposite to the running direction ofthe current. Therefore, the fuse link can be easily disconnected.Besides, a less amount of the material constituting the fuse link iscaused to migrate at the bent portion. Accordingly, providing the bentportion and the widened portion in the fuse link further facilitatesdisconnecting the fuse link.

In the semiconductor device according to the present invention, thewidened portion may be provided at a position closer to the currentinlet terminal than the bent portion. The widened portion may be locatedin the vicinity of the bent portion.

In the semiconductor device according to the present invention, thewidened portion may be provided at a generally central portion of thefuse link.

The semiconductor device according to the present invention may furtherinclude a conductor insulated from the fuse link and disposed so as tosurround the fuse link.

Providing thus the conductor that covers the fuse link causes the heatgenerated in the fuse link when a current is supplied thereto to bereflected by the conductor and detained, thus further facilitating thedisconnection of the fuse link.

In the semiconductor device according to the present invention, theconductor may include a via conductor provided at a lateral portion ofthe fuse link.

In the semiconductor device according to the present invention, thesecond fuse link may include a conductor plate provided at least on anupper side or a lower side of the fuse link.

In the semiconductor device according to the present invention, atransistor may be provided on the semiconductor substrate, so as tosupply a current to the fuse link by turning on the transistor. Here,the transistor may be a MOSFET.

It is apparent that the present invention is not limited to the aboveembodiment, and may be modified and changed without departing from thescope and spirit of the invention.

1. A semiconductor device comprising: a semiconductor substrate, and an antifuse provided on said semiconductor substrate, wherein said antifuse includes: a first link portion, a second link portion coupled to said first link portion, a first terminal and a second terminal respectively provided at an end and the other end of said first link portion, a third terminal and a fourth terminal respectively provided at an end and the other end of said second link portion, and a decision unit which is coupled to said first terminal, said second terminal, said third terminal, and said fourth terminal, wherein said decision unit is configured to decide whether both of said first link portion and said second link portion are connected and output a signal indicating that said antifuse is connected when both of said first link portion and said second link portion are decided to be connected, and to decide whether one of said first link portion and said second link portion are disconnected and output a signal indicating that said antifuse is disconnected when one of said first link portion and said second link portion is decided to be disconnected.
 2. The semiconductor device according to claim 1, wherein said first link portion and said second link portion are respectively constituted of a copper-containing metal layer predominantly composed of copper.
 3. The semiconductor device according to claim 1, wherein said first link portion and said second link portion are formed in a same size and same shape.
 4. The semiconductor device according to claim 1, wherein said decision unit decides that said antifuse is non-defective when said first link portion and said second link portion are both connected.
 5. The semiconductor device according to claim 1, wherein said decision unit which is configured to further decide whether neither of said first link portion and said second link portion is connected and output a signal indicating that said antifuse is disconnected when neither of said first link portion and said second link portion is decided to be connected.
 6. The semiconductor device according to claim 1, further comprising a first switch element provided between said first terminal and said third terminal, so as to electrically connect or disconnect said first terminal and said third terminal.
 7. The semiconductor device according to claim 1, further comprising a second switch element provided between said second terminal and said fourth terminal, so as to electrically connect or disconnect said second terminal and said fourth terminal.
 8. The semiconductor device according to claim 1, wherein said decision unit is configured to further decide whether one of said first link portion and said second link portion is connected and output a signal indicating that said antifuse is connected after the use of said antifuse is started.
 9. The semiconductor device according to claim 1, wherein said first link portion and said second link portion are connected in parallel.
 10. A semiconductor device comprising: a semiconductor substrate, and an antifuse provided on said semiconductor substrate, wherein said antifuse includes: a first link portion and a second link portion connected in parallel, a first terminal and a second terminal respectively provided at an end and the other end of said first link portion, a third terminal and a fourth terminal respectively provided at an end and the other end of said second link portion, and a decision unit which is coupled to said first terminal, said second terminal, said third terminal, and said fourth terminal, wherein said decision unit is configured to decide whether said first link portion and said second link portion are both connected, and output a result of the decision, and a first switch element provided between said first terminal and said third terminal, so as to electrically connect or disconnect said first link portion and said second link portion.
 11. The semiconductor device according to claim 10, further comprising a second switch element provided between said second terminal and said fourth terminal, so as to electrically connect or disconnect said second terminal and said fourth terminal. 